I’m hitting the following error RuntimeError: Could not infer dtype of NoneType when training a TextClassifier as follows
learn.freeze_to(-2)
learn.fit_one_cycle(1, slice(1e-2/(2.6**4),1e-2), moms=(0.8,0.7))
The error seems to happen in the fastai library. The funny things is two lines before the return we can read this comment
# XXX: Pytorch bug in dataloader using num_workers>0; TODO: create repro and report
Am I hitting this bug? if so what could be the workaround
Here is full stack trace
0.00% [0/1 00:00<00:00]
epoch train_loss valid_loss accuracy
Interrupted
---------------------------------------------------------------------------
RuntimeError Traceback (most recent call last)
<ipython-input-19-7115bd4f1526> in <module>()
1 learn.freeze_to(-2)
----> 2 learn.fit_one_cycle(1, slice(1e-2/(2.6**4),1e-2), moms=(0.8,0.7))
/usr/local/lib/python3.6/dist-packages/fastai/train.py in fit_one_cycle(learn, cyc_len, max_lr, moms, div_factor, pct_start, wd, callbacks, **kwargs)
18 callbacks.append(OneCycleScheduler(learn, max_lr, moms=moms, div_factor=div_factor,
19 pct_start=pct_start, **kwargs))
---> 20 learn.fit(cyc_len, max_lr, wd=wd, callbacks=callbacks)
21
22 def lr_find(learn:Learner, start_lr:Floats=1e-7, end_lr:Floats=10, num_it:int=100, stop_div:bool=True, **kwargs:Any):
/usr/local/lib/python3.6/dist-packages/fastai/basic_train.py in fit(self, epochs, lr, wd, callbacks)
160 callbacks = [cb(self) for cb in self.callback_fns] + listify(callbacks)
161 fit(epochs, self.model, self.loss_func, opt=self.opt, data=self.data, metrics=self.metrics,
--> 162 callbacks=self.callbacks+callbacks)
163
164 def create_opt(self, lr:Floats, wd:Floats=0.)->None:
/usr/local/lib/python3.6/dist-packages/fastai/basic_train.py in fit(epochs, model, loss_func, opt, data, callbacks, metrics)
92 except Exception as e:
93 exception = e
---> 94 raise e
95 finally: cb_handler.on_train_end(exception)
96
/usr/local/lib/python3.6/dist-packages/fastai/basic_train.py in fit(epochs, model, loss_func, opt, data, callbacks, metrics)
87 if hasattr(data,'valid_dl') and data.valid_dl is not None:
88 val_loss = validate(model, data.valid_dl, loss_func=loss_func,
---> 89 cb_handler=cb_handler, pbar=pbar)
90 else: val_loss=None
91 if cb_handler.on_epoch_end(val_loss): break
/usr/local/lib/python3.6/dist-packages/fastai/basic_train.py in validate(model, dl, loss_func, cb_handler, pbar, average, n_batch)
47 with torch.no_grad():
48 val_losses,nums = [],[]
---> 49 for xb,yb in progress_bar(dl, parent=pbar, leave=(pbar is not None)):
50 if cb_handler: xb, yb = cb_handler.on_batch_begin(xb, yb, train=False)
51 val_losses.append(loss_batch(model, xb, yb, loss_func, cb_handler=cb_handler))
/usr/local/lib/python3.6/dist-packages/fastprogress/fastprogress.py in __iter__(self)
63 self.update(0)
64 try:
---> 65 for i,o in enumerate(self._gen):
66 yield o
67 if self.auto_update: self.update(i+1)
/usr/local/lib/python3.6/dist-packages/fastai/basic_data.py in __iter__(self)
45 def __iter__(self):
46 "Process and returns items from `DataLoader`."
---> 47 for b in self.dl:
48 y = b[1][0] if is_listy(b[1]) else b[1]
49 if not self.skip_size1 or y.size(0) != 1: yield self.proc_batch(b)
/usr/local/lib/python3.6/dist-packages/torch/utils/data/dataloader.py in __next__(self)
613 if self.num_workers == 0: # same-process loading
614 indices = next(self.sample_iter) # may raise StopIteration
--> 615 batch = self.collate_fn([self.dataset[i] for i in indices])
616 if self.pin_memory:
617 batch = pin_memory_batch(batch)
/usr/local/lib/python3.6/dist-packages/fastai/text/data.py in pad_collate(samples, pad_idx, pad_first)
90 if pad_first: res[-len(s[0]):,i] = LongTensor(s[0])
91 else: res[:len(s[0]):,i] = LongTensor(s[0])
---> 92 return res, tensor([s[1] for s in samples])
93
94 def _get_processor(tokenizer:Tokenizer=None, vocab:Vocab=None, chunksize:int=10000, max_vocab:int=60000,
/usr/local/lib/python3.6/dist-packages/fastai/torch_core.py in tensor(x, *rest)
68 # XXX: Pytorch bug in dataloader using num_workers>0; TODO: create repro and report
69 if is_listy(x) and len(x)==0: return tensor(0)
---> 70 return torch.tensor(x) if is_listy(x) else as_tensor(x)
71
72 def np_address(x:np.ndarray)->int:
RuntimeError: Could not infer dtype of NoneType